JPH11320434A - Thread fastening machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a thread from being abraded and to improve workability by feeding/exhausting compressed air in a nose part, which stores a decelerating mechanism and the rear end of an anvil, synchronously with the feeding/ exhausting of the compressed air to an air motor. SOLUTION: An anvil 10 is rotated interlocked with a reduction mechanism in a nose and projects a driver bit 9 from the nose part 11 to the screwed side main body 1 outside in such a state as to store it. The nose part 11 which stores the reduction mechanism and a clutch shank 25 in the rear end of the anvil 10 is so constituted as to communicate with an inlet valve by an air passage and is communicated with a passage 6b branched from a passage 6a. A compressed air slowly flows into the nose part 11 by opening of the inlet valve 7, while being delayed synchronously to the air motor 2 and after the inlet valve 7 is closed, the compressed air is exhausted to the outside in delay. This constitution hardly release its fitting with the thread so as to hardly come it out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw driving machine using compressed air as a power source.

[0002]

2. Description of the Related Art In general, some screw tightening machines using compressed air as a power source automatically start and stop a driver bit 9 provided on the output side of an air motor 2. 6, the power of the air motor 2 is transmitted to the driver bit 9 via a planetary gear 72 or the like, which is a reduction mechanism 20, and the driver bit 9 is further tightened with a screw. The screw is slidable with respect to the machine body 1, the tip of which is engaged with the screw 30, is pressed against the material to be fastened 29, and when thrust is applied to the driver bit 9, the tip moves relative to the machine body 1. ,
The rear end pushes up the air supply valve 7 to automatically start the air supply port 4 and the passage 6a of the air motor 2 so that the screw 30 is tightened, the driver bit 9 returns, and the air supply valve 7 is closed. The air motor 2 was stopped. Further, the driver guide 12 which can adjust the movement of the driver bit 9 in the axial direction is screwed into the screw tightening machine main body 1, the length of the protrusion of the driver bit 9 from the tip of the driver guide 12 is adjusted, and the screw 30 is tightened. An adjustment stopper that can be adjusted so that the end depth is constant is used.

Accordingly, the screw tightening operation is performed after the tip of the driver bit 9 is engaged with the cross groove of the screw head 31.
When the thrust P is applied to the material 29 to be fastened, the screw 3
0, a thrust is applied to the operating rod 17 via the driver bit 9 and the air supply valve 7 is opened. Then, compressed air flows in, the air motor 2 starts, the driver bit 9 rotates, and screw tightening is started (FIG. 7A).

As the screw tightening proceeds, the screw head 31 abuts on the workpiece 29 and the tip of the driver guide 12 as a stopper at the height of the opening gap d between the workpiece 29 and the air supply valve 7 (FIG. 7). (B)). Thereafter, when the screw 30 is tightened, the screw 30 is further screwed into the workpiece 29, so that the driver bit 9 also advances. Screw tightening progresses and screw 3
When 0 is tightened by the gap d and becomes flush with each other, the air supply valve 7 is closed together with the axial movement of the driver bit 9,
The thrust is not applied to the driver bit 9, the air motor 2 stops, and the screw tightening ends (FIG. 7 (c)).

[0005]

The screw tightening machine shown in FIG. 6 is called a push start type, and has a structure in which the air motor 2 is started just by fitting the screw 30 into the driver bit 9 and pressing the main body 1. Therefore, work speed is increased and workability is good. Further, since the screw can be tightened to a certain depth by the driver guide 12, there are advantages such as good finish.

[0006] However, if a screw called a Philips type which is usually used does not always press the tip of the driver bit 9 against the cross groove of the screw head 31 with a constant load during the tightening work, the screw of its own tightening torque is not increased. Due to the reaction force, the driver bit 9 separates from the cross groove,
The cross-shaped groove may be broken and damaged, or the tip of the driver bit 9 itself may be worn at an early stage. This is generally called a come-out.

[0007] In the screw tightening machine, the screw 30 starts to be tightened by a push-start method. Therefore, when the screw 30 is fastened to a gypsum board or the like, the screw 30 must be fastened if not pressed quickly. 9
Return did not follow, and came-out sometimes occurred.

During screw tightening, since the driver bit 9 is completely retracted, the thrust P applied to the main body 1 is transmitted to the tip of the driver bit 9 as it is (FIG. 7 (a)). ). However, immediately before the screw tightening is completed, the screw head 31 is at the height of the opening gap d between the workpiece 29 and the air supply valve 7, and after the tip of the driver guide 12 abuts against the workpiece 29 as a stopper, the screw is When the screw 30 is tightened, the screw 30 is further screwed into the workpiece 29 so that the driver bit 9 continues to move forward, and the driver bit 9 is not subjected to the thrust P for pressing the main body 1. In this case, the driver bit 9 came out of the cross groove without suppressing the reaction force of the screw tightening torque. Therefore, the load of the spring 18 for returning the anvil 10 is increased to prevent the above-described cam-out. However, since a large load must be applied, the driver bit 9 is first pressed to release the air supply valve 7. The load to open also became heavy, making it very difficult to use. This come-out is more likely to occur as the tightening power of the main body 1 increases.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the structural disadvantages of the prior art screwdriver described above, improve the structural defects of the push-start type, and provide the above-mentioned prior art screwdriver even when there is a driver guide serving as a stopper. An object of the present invention is to provide a screw tightening machine which prevents screw tanning which is a drawback of the screw tightening machine and has good workability.

Another object of the present invention is to provide a screw feeding mechanism for feeding a connected screw, and when removing a screw from a connecting band of a connecting screw, a load due to compressed air is generated behind the anvil. Since the screw is extruded so as to be detached, the screw serves as an auxiliary power for detaching the screw from the connection band. Therefore, by providing a screw tightening machine capable of tightening the screw with a lighter load than a conventional connection screw driver. is there.

[0011]

The above object is achieved by supplying and discharging compressed air to and from a nose portion which accommodates a rear end of a speed reduction mechanism and an anvil in synchronization with supply and discharge of compressed air to and from an air motor. You.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing one embodiment. FIG. 1 shows a longitudinal sectional view of the screwing machine. In the figure, a screwing machine main body 1 has a nose in which an air motor 2 and a reduction mechanism 20 of the air motor 2 are built in a housing 3 having an air supply opening 4 opened. The parts 11 are arranged vertically in parallel. Air motor 2 and reduction mechanism 20
Are connected via gears 15a and 15b on the handle 5 side.

The anvil 10 is rotationally driven in cooperation with a speed reduction mechanism 20 in the nose portion 11 and has a driver bit 9.
Has a certain diameter so as to be able to be accommodated, and protrudes from the nose portion 11 to the outside of the main body 1 on the screw side. Nose part 11
, The driver bit 9 and the anvil 10 are movable in the axial direction, and are always urged by a spring 33 or the like in the screw tightening direction.
Is connected to the air motor 2 via an air supply valve 7 which is opened and closed in association with the forward and backward movement in the axial direction to start and stop the air motor 2, while the screw-side end of the housing 3 has an anvil 10 and a driver bit 9. A screwdriver guide 12 surrounding the driver bit 9 is screwed together so as to be movable or fixed in the axial direction of the driver bit 9 so as to adjustably support the protrusion length of the driver bit 9 from the nose portion 11.
The nose portion 11 that houses the deceleration mechanism 20 and the clutch shank 25 at the rear end of the anvil 10 is configured to be able to communicate with the air supply valve 7 through at least one air passage.
a through a small-diameter passage 6b branching from a.
Accordingly, the compressed air due to the opening of the air supply valve 7 slowly flows into the nose portion 11 with delay with the air motor 2, and even after the air supply valve 7 is closed, the compressed air is delayed and exhausted to the outside. did.

Next, each of the components will be described in more detail. An air supply port 4 opened at the rear end of the handle portion 5 of the housing 3 is connected to an air supply source (not shown) such as an air compressor via a hose or the like. The air supply port 4 is connected to the air motor 2 via a passage 6a, and an air supply valve 7 is provided between the air supply port 4 and the passage 6a.

The air supply valve 7 is disposed behind the driver bit 9 and the speed reduction mechanism 20, and has a cylindrical valve housing 40.
The valve stem 41 is slidably housed therein, and the valve stem 41 cooperates with a trigger 42 and a trigger arm 43 rotatable within the trigger 42 to slide the operating rod 17 operatively connected to the driver bit 9. Thus, the passage 6a connecting the air supply port 4 and the air motor 2 is opened and closed. Valve stem 4
1 is normally urged by a spring 18 toward the driver bit 9 to close the air supply port 4 and the passage 6a.
By pushing in 1, the seal is released, the passage 6 a is opened, and compressed air is supplied to the air motor 2 from an air supply source. When the pushing force of the valve stem 41 is released, the valve stem 41 returns to the original position, and the passage 6a is closed.

Switching between forward and reverse rotation of the driver bit 9 is as follows.
By rotating the valve stem 46 of the forward / reverse rotation switching valve 45 left or right, the passage 6a is connected to the air supply unit where the air motor 2 rotates in the forward rotation direction or the air supply unit where the air motor 2 rotates in the reverse rotation direction. The rotation direction of the air motor 2 also determines the rotation direction of the driver bit 9.

The air motor 2 is connected to the air supply port 4 via a passage 6a and is driven by compressed air supplied from the passage 6a. Supported as possible. A gear 15a is mounted on the rear end of the rotating shaft 8. Reduction mechanism 2
0, a gear 15b meshing with the gear 15a is provided, and the rotation of the air motor 2 is controlled by the gear 15a and the gear 15b.
The gear 15 b is provided with a gear 15 c on the outer periphery of the screw-side end of the gear 15 b, and is connected to the reduction mechanism 21.

The speed reduction mechanism 20 is an impact mechanism 19, and as shown in FIG. 2, the rotation of the air motor 2 is transmitted from the gears 15a and 15b to the gear 15c, and the gear 15c is fitted to the cam 22. In a relationship. The cam 22 is rotatably fixed to the clutch frame 21 by a predetermined angle, is rotatably supported on the clutch frame 21 by a shaft 28, and has an engagement relationship with a dog 24 having an engagement piece 23 at one end. An anvil 1 provided integrally with the clutch shank 25 by rotating the dog 24 by a predetermined angle by the cam 22 and applying an intermittent repeated impact to the working end of the clutch shank 25 by the edge of the dog 24.
Rotate 0. The impact mechanism 19 has a conventionally well-known configuration, for example, the same configuration as that shown in FIG. 2 of Japanese Patent Application Laid-Open No. 9-174448 filed earlier by the present applicant.

As shown in FIG. 3, the sealing of the nose portion 11 accommodating the impact mechanism 19 is performed by a sealing portion 51a disposed at the rear and a sealing portion 51b in the screw tightening direction.
And the O-rings of the seal portion 51c, and all of these seal portions are portions where the shaft repeatedly rotates and slides, but maintains durability so that the seal portion is completely sealed even when subjected to internal pressure. The configuration is as follows. O-ring 38a of seal portion 51a is gear 1
5b is slightly smaller than the closed shaft diameter, and has a clearance or the smallest possible interference with the outer periphery of the groove 50a of the nose portion 11 for accommodating the O-ring 38b. The O-ring 38b of the seal portion 51b is configured to be slightly smaller than the outer periphery of the shaft to seal the anvil 10, and the O-ring 3
There is a gap or the smallest possible interference with the outer periphery of the groove 50b of the nose portion 11 for accommodating 8b. Therefore, when compressed air flows into the nose portion 11, the O-ring is pressed by pressure, and the seal portion 51a is hermetically sealed by the shaft of the gear 15a and the outer periphery of the groove portion 50a or the rear end surface of the groove portion 50a. 51b can be hermetically closed by the shaft side of the anvil 10 and the outer periphery of the groove 50b or the front end face of the groove 50b.

As described above, the O-ring is pressed by the pressure of the compressed air flowing into the nose portion 11, and the outer periphery of the shaft of the gear 15b and the groove 50a of the seal portion 51a.
A frictional friction is generated between the outer periphery of the groove 50a and the rear end face of the groove 50a, and for the seal part 51b between the shaft side of the anvil 10 and the outer periphery of the groove 50b or the front end face of the groove 50b. Therefore, the transmission loss to the driver bit 9 of the rotational driving force of the air motor 2 is reduced as the interference to the outer periphery is reduced with or without the interference to the outer periphery of the shaft. Further, since the O-ring has a circular cross-sectional shape, even when sealing is performed by receiving pressure from the outer periphery, the contact portion is relatively close to a point, so that the sliding resistance is small and the abrasion hardly occurs.

Further, the O-ring 38c of the seal portion 51c is configured to be slightly smaller than the shaft diameter of the operating rod 17 housed through the gear 15b, and is provided on the front end face of the gear 15b.
The O-ring 38c is always urged by a spring 33 disposed at the rear end, so that the O-ring 38c can be sealed by the outer periphery of the operating rod 17 and the front end face of the gear 15b. Therefore, the O-ring 38c of the seal portion 51c can be hermetically sealed with the operating rod 17 while rotating integrally with the gear 15b, so that the transmission loss of the rotational driving force of the air motor 2 to the driver bit 12 is small.

Further, the nose portion 11 can communicate with the air supply port 4 through a small-diameter passage 6b branched from the passage 6a, and the compressed air from the air supply port 4 flows into the air motor 2 by the opening of the air supply valve 7. And the nose part 11 which is sealed at the same time
Since the compressed air flows with a slight delay, the pressure gradually increases and is accumulated. The nose 1 from the passage 6b
The compressed air that has entered inside 1 enters the space behind the anvil 10 through the gap between the gear 15c and the cam 22.

The side of the anvil 10 in the screw tightening direction is exposed to the outside from the nose portion 11 and is at atmospheric pressure. Further, the shaft portion is sealed by a seal portion 51b. Therefore, the rear end face of the anvil 10 receives the pressure, and a pressing load is generated by the pressure. Further, since the pressure is gradually increased and accumulated, the pressing load also becomes gradually larger.

When the air supply valve 7 is closed, the pressure in the nose portion 11 is exhausted simultaneously with the air motor 2, but the passage 6b
However, since the diameter is small, the compressed air is exhausted to the outside with a slight delay. At this time, the load due to the pressure on the rear end surface of the anvil 10 also gradually decreases.

The anvil 10 is provided coaxially and rotatable integrally with the driver bit 9.
The dog 24 rotates around the clutch shank 25 of the anvil 10 together with the clutch frame 21 due to the resistance caused by the engagement of the driver bit 9 and the screw 30 at 0, and the rotation of the dog 24 occurring during this rotation causes the dog 24 to rotate. The working end of the clutch shank 25 is hit intermittently at the edge, and the anvil 10 is gradually rotated by repeating this hitting operation.

The anvil 10 is provided with a stroke of a fixed distance so as to be able to move forward and backward in the axial direction thereof in cooperation with the driver bit 9. The air supply valve 7 is set to be opened and closed, and is always urged forward in the screw tightening direction by the spring 33 of the urging means. Therefore, after the air supply valve 7 is closed,
The anvil 10 can move a fixed distance.

At the screw-side end of the anvil 10 is formed a recess 26 in which the driver bit 9 is non-rotatably mounted. On the opposite end, a receiving portion 34 of the operating rod 17 is formed. The ball 52 is inserted so that the rotation is not transmitted to the operation rod 17. The operating rod 17 includes a gear 15
The valve stem 41 of the air supply valve 7 is provided so as to be slidably housed through the b and is operatively connected to the driver bit 9.

As described above, the anvil 10 rotates to turn the driver bit 9, enters the air supply valve 7 by retreating and opens, and retreats from the air supply valve 7 by forward movement to close the valve. The ball 2 for holding the driver bit 9 is provided in the recess 26 at the screw-side end of the anvil 10.
7 are engaged to prevent slippage.

An adjusting screw portion 13 is formed at the screwing end of the nose portion 11 at the tip of the screwing machine main body 1, and a driver guide 12 is screwed to the adjusting screw portion 13. The driver guide 12 is formed in a cylindrical shape, and a screw portion corresponding to the adjusting screw portion 13 is formed at a base portion thereof. The depth of the screw portion with respect to the nose portion 11 is fixed or moved,
The protruding length of the driver bit 9 from the nose portion 11 is supported so as to be adjustable in the axial direction. The driver guide 12 is prevented from rotating by a locking projection 37 of a locking ring 35 that can move only in the axial direction with respect to the nose portion 11, and the locking ring 35 is always urged against the driver guide 12 by a spring 36. In this state, the vehicle is normally engaged with the driver guide 12. When adjusting the driver guide 12, the locking ring 35 is moved against the spring 36 to release the engagement of the locking projection 37 so that the driver guide 12 can be rotated. The driver bit 9 is detachably provided on the anvil 10 and protrudes from the nose portion 11, but is surrounded by the driver guide 12.

Next, the operation of the screw tightening machine configured as described above will be described with reference to FIGS. In using the screw tightening machine having the above structure, the trigger 42 of the screw tightening machine main body 1 is pulled, and then the tip of the driver bit 9 is inserted into a predetermined screwed portion of the material 29 to be fastened to the cross groove of the screw head 31. Then press the body 1 together. As a result, the driver bit 9 is pushed into the screwdriver body 1 by the screw 30, and the anvil 10, the operating rod 17 and the push lever 47 rotate the trigger arm 43, and the valve stem 41 resists the force of the spring 18. Then, the air supply valve 7 connected to the air supply port 4 is opened, the air supply source 32 communicates with the passage 6a to supply compressed air, and the air motor 2 is driven.

When the air motor 2 rotates, the rotation is performed from the rotation shaft 8 of the air motor 2 to the gear 1 disposed at the rear end thereof.
5a, the gear 15b meshing with the gear 15a rotates, and the rotation can be transmitted from the gear 15c provided at the screw-side end of the gear 15b to the impact mechanism 19 as the reduction mechanism 20. The power is transmitted to a cam 22 which is in a fitting relationship with the gear 15c and is rotatably fixed to the clutch frame 21 by a predetermined angle. In addition, the working end of the clutch shank 25 is intermittently repeatedly hit by the edge of a dog 24 rotatably supported by the clutch frame 21 and having an engagement piece 23 at one end, so that the clutch shank 25 is integrally formed with the clutch shank 25. The provided anvil 10 rotates.

As a result, the driver bit 9 mounted on the anvil 10 rotates to tighten the screw 30. That is, since the resistance due to the engagement between the driver bit 9 and the screw 30 acts on the anvil 10, the dog 24 rotates together with the clutch frame 21 around the clutch shank 25, and the rotation of the dog 24 occurring during this rotation causes the edge of the dog 24 to rotate. The working end of the clutch shank 25 is intermittently struck at the portion, and a high torque torque is generated in the anvil 10 by repeating this striking operation, whereby the driver bit 9 rotates little by little to tighten the screw 30. Will go on.

Nose part 1 for storing impact mechanism 19
At the same time as the rotation of the air motor 2, the compressed air from the air supply port 4 flows through the passage 6 b with a slight delay from the compressed air flowing into the air motor 2, and the pressure inside the nose portion 11 gradually increases. Rises.

As a result, a load due to pressure is generated on the rear end surface of the anvil 10, but the pressure gradually increases and accumulates.
Is almost only the load of the springs 18 and 33. When the driver bit 9 is lightly pressed similarly to the conventional push-start type screwdriver, and the screw 30 pushes the anvil 10 into the screwdriver body 1 side, The air supply valve 7 opens,
The air motor 2 starts driving.

As the screw tightens, the nose 11
As the internal pressure increases, the load due to the pressure on the rear end face of the anvil 10 gradually increases. At this time, even if the screw 30 is tightened earlier than the follow-up of the driver bit 9, if the screw 30 is not pressed quickly when stopping on a gypsum board or the like,
The constant stroke returns because the driver bit 9 moves due to the pressure, and it is difficult to disengage the screw 30 from the screw 30, so that it is difficult for cam out to occur.

In FIGS. 3 and 4, a screwdriver body 12 is screwed into the screwdriver body 1 of FIG. 1 of the present invention, and the driver bit 9 from the tip of the driver guide 12 is screwed. Although the screwing machine in which the protruding length is adjusted so that the tightening end depth of the screw 30 is adjusted to be constant is shown, when the screw 30 is tightened by such a screwing machine, first, 1 is the same as the screw tightening machine of FIG.
The distal end of the driver guide 12 abuts against the material to be fastened 29 as a stopper, and the screw 30 is further screwed into the material to be fastened 29 as it is tightened, so that the driver bit 9 continues to advance as in the conventional case (FIG. 4).

At this time, even if no thrust for pressing the driver bit 9 against the main body 1 is applied, the pressure in the nose portion 11 sufficiently applies a pressing load due to the pressure to the rear end face of the anvil 10 as described above. Therefore, no cam-out occurs in which the driver bit 9 comes off the cross groove of the screw head 31.

At the end of the tightening, the air supply valve 7 is closed with the advancement of the driver bit 9 and the rotation of the air motor 2 is also stopped at the same time, so that the impact by the impact mechanism 20 is also stopped. The compressed air in the nose portion 11 is also exhausted to the outside of the main body through the exhaust port 53 similarly to the air motor 2 through the passage 6b. However, since the diameter of the passage 6b is small, the compressed air is slightly delayed from the stop of the air motor 2. While being exhausted, it is exhausted to the outside. At this time, the load due to the pressure on the rear end surface of the anvil 10 also gradually decreases after the screw is tightened, and becomes the same state as before the screw tightening.

As described above, when the screw 30 reaches a predetermined screwing depth, the screw tightening operation automatically stops. Therefore, regardless of the hardness of the workpiece 29, the screw 3
0 can always be screwed into the fastening member 29 to a certain depth, and the pressure in the nose portion 11 does not impair the conventional operability.
Of the driver bit 9 from the cross groove can be prevented.

The screwing amount may be changed as needed even for the same screw 30. In this case, when adjusting the depth of the driver guide 12, since the locking ring 35 is prevented from rotating by the locking projection 37, the locking ring 35 is moved against the spring 36 to move the locking ring 35. The fitting of the screw 37 is released so that the screw can be rotated.
3 may be rotated to adjust the movement of the driver bit 9 along the axial direction. As a result, the amount of protrusion of the driver bit 9 with respect to the nose portion 11 also changes, so that
In contrast, the air supply valve 7 is closed at different depths, the driver bit 9 stops, and the screwing depth can be adjusted.

The air supply valve 7 supplies or stops compressed air by opening and closing the air passage 6a leading to the air supply source based on the relative movement of the driver bit 9 with respect to the screw tightening machine main body 1. Normally, the air supply port 4 and the passage 6a are closed by being urged by a spring 18,
, The seal is released to open the passage 6a, and compressed air is supplied to the air motor 2 from an air supply source. When the pushing force of the operating rod 17 is released, the passage 6a is closed as before.

Further, in the present invention, the screw tightening machine is used in which screws are manually inserted one by one from the tip of the screw tightening machine, but as shown in FIG. 5, the screw tightening machine main body 1 of FIG. For example, U.S. Pat.
No. 2612126, a screwdriver 30 is mounted on a flexible connecting strip, so that the screw bit 63 is connected to the body 1 in order to feed the screw bit 63 into a screwing position corresponding to the driver bit 9. 9 is provided with a feed wheel 61 on a slider 60 which is relatively movable in the axial direction.
3 is engaged, the wheel 61 is intermittently rotated in response to the relative movement, and a screw feeding mechanism for screwing the screw on the connecting band 63 is adopted. Although a large load is required when the screw 30 is detached, by employing the above structure, when the driver bit 9 hits the head of the fed screw 30 and retreats, the air supply valve 7 opens and the air motor 2 starts. Simultaneously, the compressed air flows into the nose portion 11 and a load due to the compressed air is generated in the anvil 10, and this load becomes an auxiliary load when the screw 30 is detached from the connecting band 58 of the connecting screw. The screw 30 can be tightened with a lighter load than that of the connection screw driver. In addition, similar effects such as a good finish without the come-out can be obtained.

FIG. 4 is different from the above-described embodiment.
In the main body in FIG.
And Japanese Utility Model Application Laid-Open No. 61-75966,
A gear housing 73 includes a cylindrical gear 70 and a planetary gear 72 that meshes with teeth 71 provided on an inner wall of the gear 70 and the housing 3. The cylindrical gear 70 and the gear housing 73 are air motors, respectively. The cylindrical gear 70 is rotatably provided coaxially with the shaft 74. Teeth are provided around the inner and outer circumferences of the cylindrical gear 70, and the inner circumferential teeth (not shown) mesh with the teeth 75 of the air motor shaft 74. And outer teeth 7
6 meshes with the teeth 77 of the planetary gear 72. Planetary gear 7
2 is rotatably provided on the outer peripheral end of the gear housing 73 and meshes with the cylindrical gear 70 and meshes with teeth 78 formed on the inner wall of the housing 3. Therefore, the rotation of the cylindrical gear 70 is transmitted to the planetary gear 72 and further transmitted to the gear housing 73. The air motor 2 and the cylindrical gear 70 rotate at a constant speed. However, the gear housing 73 is reduced in speed by the gear ratio between the cylindrical gear 70 and the planetary gear 72 and between the planetary gear 72 and the inner wall teeth 78, and further, the anvil 10 is rotated. However, also in this mechanism, the housing 3 containing the speed reduction mechanism 20 has a closed structure as in the above-described embodiment, and the nose for storing the rear end of the speed reduction mechanism and the anvil 10 is also disclosed. The unit 11 includes the air motor 2
The air supply valve 7 is closed except for a part of the outside and communicates with the air supply valve 7 through the passage 6a, so that the compressed air from the opening of the air supply valve 7 flows into the nose portion 11 from the air motor 2, and the air supply If the system is configured to exhaust air to the outside after the valve 7 is closed, the same effect as in the above-described embodiment does not change.

[0044]

According to the screw tightening machine of the present invention, when the trigger is pulled, the driver bit is pressed as in the case of the push-start type screw tightening machine, and the air supply valve is opened, compressed air is supplied to the air motor to rotate. The screw rotates together with the driver bit, and the screw tightening operation is started. At this time, since the compressed air flowing into the air motor flows into the nose portion housing the impact mechanism with a slight delay, the pressure in the nose portion gradually increases. For this reason, a load due to pressure is generated on the rear end face of the anvil, but since the pressure gradually increases and the pressure is accumulated, the initial load on the anvil at the start of screw tightening is only the spring load as in the past, At the start of screw tightening, it is possible to press the driver bit with a light pressing force as in the related art. Therefore, when the air motor starts, the compressed air flows into the nose portion, and a constant pressing force is generated by the compressed air at the rear end of the anvil. Even if the driver bit tightens faster than the driver bit follows, a certain stroke moves the driver bit to follow the driver bit due to the pressure. It is difficult.

[0045] Even when the screwing is advanced and the tip of the driver guide abuts against the work to be fastened as a stopper, and the driver bit does not receive a thrust for pressing against the main body, the driver bit has sufficient pressing force due to the compressed air from the anvil. Therefore, no cam-out occurs from the cross groove due to the reaction force of the screw tightening torque. Since the compressed air in the nose portion is delayed and exhausted to the outside, the load on the anvil is not lost until the moment when the air supply valve is closed and the air motor is completely stopped.

Since the operation of the screw tightening machine is automatically stopped when the screw reaches a predetermined screwing depth, the screw is always kept at a certain depth with respect to the workpiece regardless of the hardness of the workpiece. You can screw it down.

As described above, the screw tightening is completed at the position where the driver guide and the driver bit cooperate, and since the driver bit does not come out of the cross groove, the fastening of the material to be fastened is stopped. Regardless of the hardness, the screw can always be screwed into the workpiece at a arbitrarily set constant depth.

Incidentally, the screwing amount may be changed as necessary even for the same screw. In this case, the adjustment screw portion of the driver guide may be rotated to adjust the movement of the driver bit along the axial direction. As a result, the amount of protrusion of the driver bit with respect to the nose portion also changes, so that the air supply valve closes at different depths with respect to the workpiece, the driver bit stops, and the screwing amount can be adjusted.

As described above, it is possible to improve the finish while preventing the screw tanning by simply fixing the screw tightening depth to the structure, and it is possible to prevent the cam out even if the screw tightening power is increased. Can be.

When a screw supply mechanism for screwing a screw on the connecting band is attached to the main body of the screw tightening machine, when the screw is removed from the connecting band of the connecting screw, the anvil is retracted, the air motor is started, and the compressed air is started. Is generated behind the anvil and is pushed out to remove the screw, and this load serves as an auxiliary power to separate the screw from the connecting band.Therefore, the screw can be tightened with a lighter load than the conventional connecting screw driver. Similar effects such as what can be achieved and the above-described good finish without come-out are also exhibited.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the screw tightening machine of the present invention.

FIG. 2 is an enlarged sectional view showing a nose part of FIG. 1;

FIG. 3 is a sectional view showing another embodiment in which a driver guide is provided in the screw tightening machine of FIG. 1;

FIG. 4 is a partial sectional view showing a screw tightening operation by the screw tightening machine of FIG. 3;

FIG. 5 is a sectional view showing another embodiment in which the screw tightening machine of FIG. 1 is provided with a screw supply mechanism.

FIG. 6 is a sectional view showing an example of a conventional screw tightening machine.

FIG. 7 is a partial sectional view showing an example of a screw tightening operation of a conventional screw tightening machine.

[Explanation of symbols]

1 is a screwdriver body, 2 is an air motor, 3 is a housing, 4 is an air supply port, 6a and 6b are passages, 7 is an air supply valve, 9 is a driver bit, 10 is an anvil, 11 is a nose part, 1
2 is a driver guide, 20 is a speed reduction mechanism, 58 is a connecting band,
59 is a screw supply mechanism, 60 is a slider, 63 is a connection screw band, 65 is a spring, and 66 is a casing.

Claims (3)

[Claims] 1. A housing provided with an air supply port connected to a compressed air source such as a compressor, a nose portion provided in the housing for accommodating an air motor and a reduction mechanism of the air motor, and rotating through a reduction mechanism. An anvil that is driven and supported in the housing so as to be able to advance and retreat, and whose tip projects out of the screw-side housing from the nose portion, a driver bit mounted on the anvil, and is provided between the air supply port and the air motor. An air supply valve that is opened and closed in association with the axial movement of the driver bit, presses the driver bit tip against a screw, opens the air supply valve, supplies compressed air to the air motor, and rotates the air motor to reduce the speed. Screw through the anvil and driver bit,
A screw tightening machine that closes an air supply valve and stops rotation of an air motor by advancing a driver bit at the time of screw tightening completion, wherein compressed air to the air motor is supplied to a nose portion that stores the reduction mechanism and a rear end of an anvil. A screw tightening machine characterized in that compressed air is supplied and discharged in synchronization with supply and discharge. 2. The screw tightening machine according to claim 1, wherein an area of a passage for supplying and discharging compressed air into the nose portion is smaller than an area of a passage to an air motor. 3. A screw-in end of the housing,
2. The screw tightening machine according to claim 1, wherein the driver guide surrounding the driver bit can be moved or fixed in the axial direction of the driver bit, and the length of protrusion of the driver bit from the housing can be adjusted. 3. A screw-in end of the housing,
A slider having a screw supply mechanism for holding a connecting screw band in which screws are arranged at a predetermined interval on a flexible resin connecting band so as to surround a driver bit, and sequentially transferring the connecting screw band to the tip of the driver bit. 2. The screw tightening machine according to claim 1, further comprising: a casing that urges the slider with a spring so as to protrude from the tip end by a specific length, and supports the slider to retract when the screw is tightened.